This application claims the priority of Korean Patent Application No. 2003-13612, filed on Mar. 5, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to digital broadcasting, and more particularly, to a method and apparatus for detecting a format of closed caption data automatically and displaying the caption data.
2. Description of the Related Art
An Advanced Television Systems Committee (ATSC) standard has been used as a digital terrestrial broadcast standard in the U.S.A. Also, the ATSC standard has been used as a standard digital terrestrial broadcasting system in the Republic of Korea.
Closed caption data is information on character data contained in a broadcast signal or a video signal and also includes information on a format of displaying the character data on a screen displayed to a user. There is a difference between a method for providing a subtitle by inputting the subtitle on a broadcast screen and setting the subtitle as a part of a screen data, which is one method for providing a subtitle to a broadcast screen, and a method for providing closed caption data, in that in the latter case, closed caption data is extracted from a broadcast video signal, synchronized with contents of a screen displayed to a user, and displayed to the user. If the user does not want to see the closed caption data or a broadcasting display device (e.g., television (TV)) does not support the closed caption data, the subtitle may not be displayed on the screen.
There are two standards for including closed caption data or closed caption information in a broadcast signal, such as Electronic Industries Association-608 (EIA-608) and Electronic Industries Association-708 (EIA-708). An ATSC standard supports both EIA-608 and EIA-708 standards.
A conventional digital TV for supporting both EIA-608 and EIA-708 standards basically supports closed caption data according to the EIA-708 standard. It is considered that all closed caption data contained in an input broadcast signal is coded according to the EIA-708 standard, and the closed caption data is decoded, and caption data is displayed to a user. The user changes a method for decoding closed caption data into the EIA-608 standard using a remote controller such that the closed caption data is decoded according to the EIA-608 standard and caption data is displayed to the user.
In other words, in the conventional digital TV, in general, when the closed caption data is decoded according to the EIA-708 standard and displayed to the user and closed caption data defined by the EIA-608 standard is contained in the broadcast signal and received, the caption data displayed to the user is not normal. The user should change a method for decoding closed caption data for a digital TV into the EIA-608 standard such that a TV decodes the closed caption data according to the EIA-608 standard and displays caption data to the user. If a broadcast signal including closed caption data defined by the EIA-708 standard is received, the user should change the method for decoding the closed caption data into the EIA-708 standard again.
Thus, if closed caption data defined by the EIA-708 and EIA-608 standards are together or alternately contained in a broadcast signal input into a digital TV (for example, closed caption data defined by the EIA-708 standard is contained in over-the-air broadcasting, but closed caption data defined by the EIA-608 standard which is a conventional standard, may be contained in cable broadcasting.), the user should change a method for processing closed caption data manually whenever closed caption data defined by a different standard is received. In this regard, the user can identify that contents of caption data displayed on a screen are abnormal.
In the prior art, the user knows that closed caption data is contained in a broadcast signal, according to information, such as caption descriptor, contained in program specific information (PSI)/program and system information protocol (PSIP). However, when the broadcast signal including the closed caption data is received, but information, such as caption script, which is simultaneously transmitted with the broadcast signal and has a different transmission bandwidth, is not received due to other causes, the caption data cannot be displayed on the screen.